The present invention relates to patient transfer devices and more particularly to a patient transfer apparatus which employs an air bearing to facilitate the transfer.
One class of device used for moving patients to and from a hospital bed, X-ray table, operating table, or the like employs a planar air pallet embodiment of an air-bearing. An air-bearing provides a layer of air between two surfaces and thereby facilitates movement of the surfaces relative to one another. Several examples of patient mover devices employing air bearings can be found in U.S. Pat. No. 4,528,704 to Wegener et al.
One Wegener et al embodiment includes a top sheet 12, a middle sheet 14, a bottom sheet 16, and a semi-rigid sheet 18. The top, middle, and bottom sheets are thin flexible sheets 12, 14, and 16, and may be formed of an electrically conductive sheet material which has a nylon scrim and a vinyl coating on both sides so as to embed the scrim within the vinyl. The thin flexible sheets 12, 14, and 16 are sewn together at predetermined positions to create sealed chambers or cavities. One such cavity 22 is formed between top sheet 12, and middle sheet 14, while a plenum chamber 24 is formed between middle sheet 14 and bottom sheet 16. The semi-rigid sheet may be a board 18 formed of plastic or the like. Board 18 is inserted into cavity 22 and extends less than the length and width of cavity 22 by about one-half inch to each side. Thousands of small pinhole-sized perforations 56 are formed in a portion of bottom sheet 16 and extend into plenum chamber 24. The gaps 40 between side edges 18b of semi-rigid sheet 18 and the sides of cavity 22 provide flexibility sufficient to produce pillowing of bottom sheet 16 inwardly of laterally spaced longitudinally extending stitching 30. Further, in the areas internally of stitchings 30, 32, and 34 defining plenum chamber 24, and externally of the modified diamond shaped area of perforations 56, bottom sheet 16 will pillow about the legs and about the shoulders and head of the patient tending to cradle the patient. This is particularly facilitated by the semi-rigid nature of sheet 18. Perforations 56 should underlie semi-rigid sheet 18 only, which functions to distribute the load over the air bearing. However, once the patient is moved and the air source disconnected, the patient rests against the semi-rigid sheet 18. This can cause discomfort and distress to patients having sensitive skin conditions.
Another example of a patient mover is disclosed in FIG. 4 of U.S. Pat. No. 4,528,704 to Wegener et al and a series of individual tubes 72, 74 instead of semi-rigid sheet 18. Tubes 72, 74 are sealed along their longitudinal sides and at both ends to form sealed chambers 76, which may be pressurized to a relatively high pressure (5 to 25 psig) via suitable valves such as individual inner tube type valves 78 for each chamber 76. Thus, tubes 72, 74 are pressurized by a separate source than supplies air under pressure to plenum chamber 24. The high pressure air filled tubes 72, 74 are substantially rigid and thus form a generally rigid backing member intermediate of a patient and plenum chamber 24. However, the requirement for the availability of a second air source which is a source of high pressure air cannot always be met. Moreover, the provision of inner tube type valves 78 can cause a hazardous condition for a patient which has a sensitive skin condition (as would a burn patient or a patient suffering from bed sores). Furthermore, the high pressure air source needs to be applied to each chamber 76 individually, and this is time consuming. In addition, the sequential inflation of chambers 76 could influence the patient to roll off the tubes or otherwise discomfort the patient.
Yet another embodiment of a patient mover 10'' is shown in FIG. 5 of U.S. Pat. No. 4,528,704 to Wegener et al and includes a top sheet 12 which is typically formed of material that will be considerably thicker and more rigid than the material forming top sheets 12 of the other embodiments of this Wegener et al U.S. Pat. No. 4,528,704. A bottom sheet 16 bears perforations 56 and forms a plenum chamber 24 with a middle sheet 14. Top sheet 12 is sealed at laterally spaced positions along longitudinally straight lines as at 70 to form a plurality of relatively large diameter tubes 80, which individually or jointly receive a flow of low pressure, low CFM air through inlet 46 which opens directly to the interior 82 of a transverse manifold 83 leading into tubes 80 via tube inlets 46'. The low CFM air flows into one end of each tube 80 bearing the inlet 46 to its opposite end, wherein an outlet as at 84 is formed within middle sheet 14. Each outlet 84 for each tube 80 should be considerably smaller than its inlet 46 and opens directly to plenum chamber 24 for pressurization of plenum chamber 24. However, once the patient is moved and the air source disconnected because no longer needed for the air bearing, tubes 80 lose their supply of air and deflate. If the patient is left on the patient mover for any length of time after the air source is disconnected, the patient could develop bed sores if the patient mover rests on a hard surface. Moreover, all of tubes 80 fill simultaneously and could dislodge the patient from the surface of the top sheet and injure the patient.